Tobacman Larry S
Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
Adv Exp Med Biol. 2008;644:85-94. doi: 10.1007/978-0-387-85766-4_7.
Tropomyosin molecules attach to the thin filament conjointly rather than separately, in a pattern indicating very high cooperativity. The equilibrium process drawing tropomyosins together on the actin filament can be measured by application ofa linear lattice model to bindingisotherm data and hypotheses on the mechanism of cooperativity can be tested. Each end of tropomyosin overlaps and attaches to the end ofa neighboring tropomyosin, facilitating the formation of continuous tropomyosin strands, without gaps between neighboring molecules along the thin filament. Interestingly, the overlap complexes vary greatly in size and composition among tropomyosin isoforms, despite consistently cooperative binding to actin. Also, the tendency of tropomyosin to bind to actin cooperatively rather than randomly does not correlate with the strength ofend-to-end binding.By implication, tropomyosin's actin-binding cooperativity likely involves effects on the actin filament, as well as direct interactions between adjacent tropomyosins.
原肌球蛋白分子以协同性非常高的模式共同而非单独地附着于细肌丝。可通过将线性晶格模型应用于结合等温线数据来测量肌动蛋白丝上原肌球蛋白聚集在一起的平衡过程，并且关于协同机制的假设也可以得到检验。原肌球蛋白的每一端都与相邻原肌球蛋白的末端重叠并附着，这有利于形成连续的原肌球蛋白链，沿着细肌丝相邻分子之间没有间隙。有趣的是，尽管原肌球蛋白同工型与肌动蛋白的结合始终具有协同性，但重叠复合物在大小和组成上差异很大。此外，原肌球蛋白协同而非随机结合肌动蛋白的倾向与端对端结合的强度无关。这意味着，原肌球蛋白与肌动蛋白结合的协同性可能涉及对肌动蛋白丝的影响以及相邻原肌球蛋白之间的直接相互作用。
